Volume control system for radioreceivers



2 Sheets-Shee'fl l V V u V E. R. HENTSCHEL VOLUME CONTROL SYSTEM FOR RADIORECEIVERS Filed Aug. l2, 1950 Hlm. .F

`uly 4, 1933.

July 4, 1933 E. R. HENTscHEL VOLUME CONTROL SYSTEM FOR RADORECEIVERS Filed Aug. 12, 1950 2 Sheets-Sheet 2 BY *(WQLNML 1TTORNEY Patented July 4, 1933 narrar VOLUME CGNTEL SYSTEM FOR RADOREOEIVERS application filed August l2, 1930.

My invention relates broadly to a radio receiving system and more particularly to a volume control circuit for radio receivers.

One of the objects of my invention is to provide a simplified system of volume control for a. radio receiving circuit.

Another object of my invention is to provide an inexpensive form of volume control. device for radio receivers wherein energy for operating the volume control mechanism may be obtained from the output of the deH tector circuit of the receiver.

Still another object of my invention is to provide a circuit arrangement for the output system of a detector in a radio receiver', by which taps may be taken to a volume control device for operating a detuning mechanism in the receiver for modifying the tuning characteristics of the receiver under conditions Where the volume of the reproduced sound tends to increase according to fading effects.

A further object of my invention is to provide a construction of detuning device adapt-- ed to be automatically actuated by the incoming signaling energy for modifying the tuning of the receiver for any particular frequency, when the signaling energy tends to increase in amplitude under the eects of fading.

A still further object of my invention is to provide a method of automatically varying the coupling between the radio frequency energy pick-up circuit and the receivcrin a radio broadcast receiving system, according to the amplitude of the incoming signaling energy, whereby effects of fading do not tend to change the volume of the reproduced sound.

@ther and further objects of my invention reside in the construction of an automatic coupling device for radio receiving circuits operative in accordance With the amplitude of the incoming signaling' energy, as set forth more fully in the specification hereinafter following by reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic showing of a. radio receiver equipped With the volume control device of my invention Fig. 2 is a side Serial No. 474,779.

elevation of the volume control mechanism with parts shown partially in cross-section; Fig. 3 is a lateral cross-sectional view through the volume control device on line 3 3 of 2; Fig. l is a lateral cross-scc tional View through a` fragmentary portion of the volume control device on line l-AI of Fig, 2; and Fig. 5 is a characteristic curve showing the principle of operation of the volume control device of my invention.

My invemzion is directed to a method for controlling the amount of energy fed to a receiver from an antenna. by making use of the fact that the plate current in a detector varies with changes in strength of signals.

Figure 1 shows a schematic diagram of a receiver, including one stage of radio frequency amplification 1 using a shield grid tube, although more stages may be used; a detector 2 of the highly biased grid type, and two stages of audio frequency amplification, indicated by reference characters 3 and 4. Alfter passing through the primary 5 of transformer 6, the plate current from detector 2 is led through the control Winding 7 of the device Which controls the capacity of the condenser 8 in the antenna-ground circuit 9-10. Condenser 11 provides an audio frequency by-pass path and condenser 12 providesa radio frequency by-pass path.r This control device is shown more in detail in Figs. 2, 3 and t. IThe apparatus includes a permanent magnet 13 terminating in oppositely directed pole pieces 13a and 13?), With an armature 11i rotatably mounted between the oppositely directed pole pieces. The armature la carries al coil 15 of many turns of tine Wire. A plate member 16 is connected to the rotatable shaft 17 on which armature 14C is mounted. Shaft 17 is journaled at 18 and 19 in jevveled bearings and is tensioned by means of spiral springs 20 and 41 supported on members 2l and 42 which are in turn carried by supporting member 22. The plate 16 is divided into an inductor damper portion 16a and a capacity area 16?), insulated one fromthe other by member 16e. rEhe portion of shaft 17 which carries plate 16 is insulated from the portion which carries coil by means of .sleeve 23. The plates 16a and 16?) are balanced on each side of shaft 17. Plate 16 is as light as possible. 24 represents the fixed plates of the condenser, which is condenser 8 of Fig. 1. There may be more than one movable plate or capacity area 16?) which is interleaved with the plates Q4 as shaft 17 is revolved. There is one more fixed plate than there are movable ones, in order to get the largest capacity variation with the least weight of moving parts.

lVhen no signal is coming in, the movable plate 1Gb 1s in a position wholly betweenv plates Q4 and the current through the coil 15 is the current Il of Fig. 5, which is the usual representation of the relations existing between grid voltage and plate current in a vacuum tube. Now, when signal eg is impressed on the grid of this tube, the plate current follows curve z'p, and so the average value rises to the value I2. This increased current in coil 15, causes the shaft to rotate the movable plate 16a toward the position shown in Fig. 3, and thus the capacity of condenser 8 is decreased and the energy fed to the receiver is decreased.

The .point at which the cont-rol begins to be effective can be varied by adjusta-bly rotat ing the fixed plates 24 with respect to the movable plate 16a. Plates 24 are to be wider than plate 16h, so that plate 16?) may rotate a few degrees before the capacity of the condenser is changed. The movable plate 16a extends between the pole pieces 31 of the damping magnet 32, supported on members and 22. The sensitivityv of the receiver may be adjusted to suit varying conditions, by the orienting of the fired plates 24 through segment-al gear 25, through helical gear 26 controlled by rota-table shaft from knobs 28 thus varying the normal value of capacity in antenna coupling condenser1 8. The segmental gear 25 is carried by segment 26 which is pivoted around jeweled bearing 19. Segment 26 carries vertical supports 29 and 30 on which stationary plates 24 are mounted.

Although a specific volume control condenser is shown in a definite location for varying the coupling of the receiver with re spect to the radio frequency pick-up circuits, other methods may be used. For instance,

lthis condenser could be used for dctuning a tuned circuit in the amplifier, or some other rotating volume control may be operatedby the device shown. If more energy is required, a direct current amplifier may be used to increase the control current. This method de- This method may be vapplied to the gridV condenser and grid leak detector. Tnasmuch as the plate current in detectors of this character decreases when the signal increases, the connections to the armature coil on the control device would have to be reversed, so as to rotate the control condenser in the right direction.

It is possible to connect a battery across the terminals of the armature of the condenser control device, so as to balance out some or all of the current when the incoming signal is weak. This will decrease the current carried by the armature coil, and permit making the device more sensitive to small changes in current.

Thilo rl described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

lVhat I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A radio receiving system including a radio frequency amplifier, a detector and an audio frequency amplifier, a radio frequency energy pick-up circuit connected with said radio frequency amplifier, an electromagnetic device connected in series with the output circuit of said detector, a variable impedance disposed in said radio frequency energy pick-up circuit, said electromagnetic device operating to vary the value of said impedance according to the amplitude of the energy delivered in the output circuit of said amplifier, and electromagnetic damping means mounted on said electromagnetic device but electrically insulated therefrom for damping the response of said electromagnetic device.

2. A radio receiving system including a radio frequency amplifier, a detector and an audio frequency amplifier, a radio frequency energy pickup circuit connected with said radio frequency amplifier, an electromagnetic device connected in series with the out` put circuit ofsaid detector, a var'able condenser disposed in said radio frequency en` ergy pick-up circuit, said electromagnetic dcvice operating to vary the setting of said variable condenser according` to the ampli tude of the energy delivered in the output circuit of said detector, said electromagnetic device being electrically insulated from said condenser.

3. Volume control means for radio receivers comprising in combination with a tuned receiving circuit, a radio frequency cnergy pick-up circuit delivering signal energy to the input of said tuned receiving circuit, means for variably controlling the tuning of said radio frequencypicleup circuit, said means including a variable condenser and an electromagnetic device for varying the effective capacity of said condenser according to the amplitude of energy delivered in the output of said tuned receiving circuit, said electromagnetic device being electrically insulated from saidfcondenser.

Volume control-means for radio receivers comprising, in combination with `a tuned receiving' circuit, a radio-frequency energy pick-up circuit delivering signal energy to the input of said tuned receiving?r circuit, a variable condenser connected to adjust the tuning'` of said pick-up circuit, and means including' an electromagnetic device insulated from saidvariable condenser for actuating said variable condenser, said means being responsive to variations in the amplitude of the output energy of said tuned receiviua` circuit.

5. Volume control means for radio receivcomprising` in combination radio frequency energy pick-up circuit, ay tuned cn'- cui having its input connected to said pickup circuit, a detector connected with said tuned circuit, a variable condenser for controlling the tuning of said radio frequency pica-up circuit, and an electro dynamic device comprising a winding' connected 1n series with the output circuit of said detector and a moving element for variably controlling' the edective capacity' of said condenser for correspondingly controllingl the tuning,` of said radio frequency energy pick-up cn'- cuit, said moving element being insulated from said condenser.

6. Volume control means for radio receivers comprisingl in combination, a radio frequency energy ji 'cli-up circuit, a tuned receivingl circuit, a detector connected therewith, a variable condenser connected with said radio frequency energy pick-up circuit and controllable in its effective capacity for varying' the electrical characteristics of said radiofrequency energy pick-up circuit, a movable actuator connected in series with the output circuit of said detector, a rotatable .shaft member interconnecting said movable actuator and said variable condenser. and means insulated from said condenser for damping' the movement thereof in accordance with the amplitude of incoming signaling' energy.

7. Volume control means for radio receivers including a radio frequency energ`A pick-up circuit, a` tuned circuit having its input connected therewith, a detector connected to the output of said tuned circuit, a

' condenser disposed in said radio frequency energy pick-up circuit and adjustable between limits for adjustingl said tuned radio receiving circuitwith respect to said raido frequency energy pick-up circuit, an angularly movable shaft member connected with said condenser, and an electromagnetic driver having' a. winding,` connected with the output of said detector. said driver operating` to angularly rock said shaft in accordance with the vamplitude of the energy delivered in the output of said detector, and means for insulating` said driver from said condenser.

8. Volume control means for radio receivers including a radio frequency enecg'y pick-up circuit, a tuned circuit having' its input connected therewith, a detector connected with the output of saidtuned circuit, a condenser disposed in said radio frequency energy pick-up circuit and adjustable between limits for adjusting' said tuned radio receivino' circuit with respect to said radio frequency energy pick-up circuit, an angularly movable shaft member connected with said condenser, an electromagnetic winding connected with the output of said detector, an armature for said winding' mounted to actuate said shaft for angularly rocking said shaft in accordance with the amplitude of the energy delivered in the output of said detector, means ext-ending` from said condenser and insulated therefrom and means disposed adjacent said last mentioned means for electrically damping the movement of said condenser.

9. Volume control means for radio receivers includingr a radio frequency energy pick-up circuit, a tuned circuit having its input connected therewith, a detector connected with the output of said tuned circuit, a. condenser disposed in said radio frequency energy pick-up circuit and adjustable between limits for varyingthe tuning' of said radio frequency energj,7 pick-up circuit, an angularly movable shaft member' connected with said condenser, an electromagnetic winding connected with the output of said detector, an armature for said winding mounted to automatically aetuate said shaft for angularly rocking' said shaft in accordance with the amplitude of the energy delivered in the output circuit of said detector, said shaft comprising an insulating' link electrically insulating said armature from said condenser and vernier means for selectively orienting' a portion of said condenser for choosing' the amplitude of signal at which the automatic control of saidradio frequency energy pickup circuit is put into operation.

10. Automatic volume control means for radio receiving circuits comprising a variable condenser having` a rotatable shaft carrying a rotor plat-e adapted to be angularly shifted with respect to a stator plate, means for selectively adjusting' the position of said stator plate to determine the output energy level at which said control means becomes initially effective, an electromagnetic actuator connected with said shaft for imparting' angular movement thereto, and an electrical damper located adjacent said rotor plate and insulated therefrom for controlling the rate of movement thereof.

l1. Automatic volume control means for radio receiving` circuits comprising ai radio .frequency amplifier, a detector having its 12. Automatic volume'control means for radio receiving circuits comprising a radio frequency amplifier, a detector having its i11- put connected to the output of said radio frequency amplifier, a radio frequency cn- J' ergy pick-up circuit delivering signal energy to the input of said radio frequency amplier, a variable condenser connected in said pick-up circuit comprising a stator and a rotor, means including an electromagnetic device for actuating said rotor and adjusting means for varying the setting of said stator. ERNEST R. HENTSCHEL. 

